A major block to the advancement of GaAs device technology is the difficulty of passivating exposed GaAs surfaces. Unlike silicon, whose oxide passivates the silicon surface leaving a low density of interface states, gallium arsenide does not have a passivating native oxide. Indeed, the interface between GaAs and its native oxide can be laden with defects which create a large interface state density in the mid band gap. This large density produces a high recombination velocity and Fermi level pinning which, in turn, deteriorate device performance. Specifically, the large interface state density produces excessive leakage currents in field effect transistors and photodiodes.
Considerable efforts have been made to improve the poor electronic properties of GaAs surfaces and GaAs-insulator interfaces, but no wholly acceptable technique has yet been achieved. Wet processing techniques are generally incompatible with the trend in integrated circuit manufacturing toward clustered dry processing. The dry processing techniques thus far proposed, require either elevated temperatures incompatible with prior formed device structures or ion bombardment which is deleterious to the long term stability of the treated surface. Accordingly, there is a need for an improved process for dry plasma passivation of gallium arsenide surfaces without heating and ion bombardment.